Continuously variable transmission (CVT) arrangements in powertrains for use in vehicles such as cars and other machines are known. A typical CVT is a device that can assume almost an infinite number of effective gear ratios between maximum and minimum values between an input shaft and an output shaft of the powertrain in which the CVT is installed. In certain applications, this capability of the CVT allows the input shaft, for example, an engine, to operate at a constant speed while traction elements of the powertrain can rotate at variable speeds.
Various known CVT types include variable diameter-pulley (VDP) or Reeves-type, toroidal or roller-based, magnetic, infinitely variable, ratcheting, incremental, radial roller, cone roller, and other drive arrangement types. In certain drive arrangements, for example, a cone roller-type, a belt is disposed around portions of two cones, which are disposed in parallel to one another, with their bases on opposite sides. The belt is slidable over and frictionally engages the external surfaces of the cones such that rotation of one cone, for example, by the input shaft, rotates the other cone, which operates to drive the output shaft. Motion or translation of the belt along the two cones together results in a gear ratio being created therebetween.
Such and other known CVT drive arrangements usually have low power transmission efficiency, for example, less than about 90%, but are still widely used because they can provide a cost-effective power transmission solution and enable the engine to run at its most efficient revolutions per minute (RPM) for a range of vehicle speeds. Additionally, CVT arrangements also enable performance enhancement for the powertrain in which they are installed by allowing the engine to turn at the RPM at which it produces peak power. This is typically higher than the RPM that achieves peak efficiency. Finally, a CVT does not strictly require the presence of a clutch, which simplifies the powertrain.